The present invention involves a process of manufacturing an elongated object by spinning at least one thread or band with a curable matrix on a core element, where the thread or band is carried by a spool and the spool is rotating around the core element at the same time as the elongated object or the spool moves chiefly in one specific length direction, so that the elongated object is constantly pulled out of the core element. The thread/s or band/s will now constitute a three-dimensional web from the inner to the outer diameter of the tube with a specified length.
The process is particularly well suited for manufacturing tubes and protective sleeves or reinforcing covers for bundles of tubes and/or cables, but can also be used for manufacturing objects of finite forms where strength is a critical factor, such as aeroplane wings or windmill blades.
Protective sleeves are vital for bundles of tubes and cables deployed on the seabed, as such tubes and cables may easily be damaged by fishing equipment, anchors and other objects being dragged along the seabed. Today protective sleeves manufactured in lengths of a few metres are used. These are strapped on to the tube or cable as they are deployed out into the sea. An example of this is shown in NO323381. This method of adapting a protective sleeve is very work demanding and slows down the deployment considerably, at the same time making quality assurance very challenging.
There are several examples of manufacturing tubes continuously as they are being deployed. Examples of this are shown in GB 1489186, U.S. Pat. Nos. 2,605,202, 3,532,132, 4,721,410, 4,183,724, 1,084,158, 4,345,854, 2,718,684, 4,651,914 and 5,062,737.
Most of these examples are concerned with the continuous pouring of concrete pipes. In many cases the use of concrete for making a protective sleeve is not a good solution. The concrete needs considerable time to harden, and this slows down the deployment. Concrete is also heavy, creating the need for big vessels for such deployment.
U.S. Pat. No. 4,558,971 describes continuous manufacturing of plastic tubes. With this method a band is wound around an internal stem by several spools with bands in a resin matrix circulate around the stem. The spools wind the band in opposite directions, whereby a pattern of crossing bands is achieved.
The bands are wound in such a way that the reels that are first in the spool will place their band at the innermost part of the tube, whereas the reels that are last in the spool will apply their band at the outermost part. This will give the tube a layered structure which gives a risk of delamination of the tube's wall that leads to a tube of relatively low strength.
Furthermore it is—because of the internal stem—not possible to wind the tube as a protective sleeve covering a tube or a cable. The finished tube may therefore only be used as a reinforcement of an existing object.
The publication GB 1228244 basically describes the ordinary machine used today for manufacturing fibre tubes. The tubes may be conical or straight. In the publication there is a drawing of a conical core element which gives a conical tube, e.g. for lighting poles. These products are of specific length identical to the length of the core element. In the illustration the core element is attached in both ends (supporting pins 14 and 16), and 16 is also attached to an engine.
According to GB 1228244 a thread is wound from one end to the other, where it turns and winds another layer on top of the previous one as it returns to the starting point. The fact that the core element 10 is conical does not influence that, but it gives a conical product. If the core element is straight, you will get the same function. This gives a static cross pattern where the only thing that can be adjusted is the crossing angle between the separate layers of the product.
GB 1228244 has an engine 18 connected to supporting pin 16, which gives a rotation to the core element 10 so that the fibres may be wound upon the product. The use of such a rotation would make it impossible to manufacture tubes for deployment directly into the sea or into the terrain.
The machine according to WO 9803326 produces a tube with a pattern almost identical to that of the above commented GB1228244, and it, too, does not spin in a 3D pattern.